The invention relates to a process for the preparation of a layered, clay-like material using a silicon oxide containing material in a finely divided state as a starting material.
It should be noted that the clay minerals occurring in nature are generated through the erosion of rocks and sediments. Such erosion processes appear to be accellerated under hydrothermal conditions.
Thus, such a hydrothermal process is known from GB-A-1- 560 504, wherein by hydrothermal treatment of igneous rocks, clay-like materials are obtained.
On the other hand, the synthesis of a layered material under hydrothermal conditions is also known. The Derwent abstract AN 91-183100, week 9125 & JP,A,3 112 808, disclose the hydrothermal synthesis of a layered silicate. More specifically, an amorphous silica-containing material, an alkali metal source, water and alcohol are according to these references reacted under hydrothermal conditions at at least 150.degree. C. A source of alumina or of magnesia can further also be present.
Hydrothermal processes nevertheless require special equipments.
Clay materials are responsible for many natural conversion processes, including reactions involving oxidation and hydrolysis. They can bind heavy metals because they have a net negative charge, which is compensated by interchangeable cations. In nature these are mainly the ions of alkaline earth metals.
On the other hand, it is possible to modify clay minerals such that their original affinity will change from hydrophilic to hydrophobic. Because of that the clay becomes suitable for the adsorption of organic compounds which dissolve poorly in water.
At the moment a very important application of clay, whether it has been modified or not, lies then in the field of the immobilization of polluted industrial waste material, in which the waste material is adsorbed by the clay and then isolated by incorporation into a cement matrix.
Due to the growing amount of industrial waste material as well as the requirements, which are becoming more and more strict, concerning the amount of waste material allowed to be discharged into the environment, there is an increasing need for a clay-like material that also has the capacity to absorb different substances that clay inherently possesses.